1. Field of the Invention
The present invention relates to malfunction diagnostic circuits for resolver wire breakages.
2. Description of the Related Art
FIG. 5 is a circuit diagram illustrating a configuration of a conventional resolver malfunction diagnostic circuit. A resolver malfunction diagnostic circuit is disclosed, in which a resolver-signal inputting circuit is configured such that a differential amplifier 10 receives signals through buffer circuits 6 and 7 from a resolver 1, which outputs, in response to rotation of a rotor, rotational-angle signals (sin θ·f(t) or cos θ·f(t)) corresponding to the rotational angle from output windings 3, and, when the output windings 3 are broken (refer to patent document 1), a wire-breakage detecting signal, which has a higher value than the maximum value obtained from the rotational-angle signals (sin θ·f(t) or cos θ·f(t)), is outputted from the differential amplifier 10, by DC bias being applied to the output windings 3.
[Patent document 1] Japanese Laid-Open Patent Publication 131,096/2000.
In such a conventional resolver malfunction diagnostic circuit, bias resistors RBU and RBL, which, in an abnormal state, may make the voltage between the terminals of the output windings deviate from the normal range, have additionally needed to be provided.
An objective of the present invention, which has been made to solve the foregoing problem, is to perform malfunction diagnosis for wire breakages of resolver output windings using a simple circuit configuration, realize the cost down and the reliability improvement for resolver malfunction diagnostic circuits, and reduce electric-power consumption therein.